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Baldwin SD Touchweight Quandry

  • 1.  Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-24-2023 08:54

    My friend and fellow RPT Russell Schmidt asked for my input on rebuilding the action on a Baldwin SD-1 (1937), the predecessor of the SD-6, the predecessor of the SD-10. It was rebuilt about 30 years ago with a new soundboard, block etc. by the late Claire Davies, a well respected local rebuilder.

    The complaint has been that the piano is difficult to play and has no dynamic range. Indeed, when I played it I immediately thought, "Boy ,there's a lot of inertia in there." It feels very heavy. It seemed like a classic case of too-heavy hammers. I expected to find keys full of lead to compensate. Measurably, the touch is quite light (45 to 50 DW).

    However, the keys turned out to have little lead and hammer strike weight is in medium range.

    I did David Stanwood's test of temporarily setting C4 front weight to 27 and finding the hammer strike weight that gets you 38 balance weight. The existing C4 hammer tested to be the perfect weight.

    SOMETHING ELSE IS GOING ON HERE!

    I happened to have a set of original hammers and shanks from a 1965 SD-6 and compared the two. The hammers on our SD-1 are further out on their shanks. Also, note 1 measures to be further out on its shank than #88.  Have the bass strike points wandered from their original specs?

    Any other ideas?



    ------------------------------
    John Pope
    University of Kentucky School of Music
    Lexington, KY
    ------------------------------


  • 2.  RE: Baldwin SD Touchweight Quandry

    Posted 05-24-2023 09:26

    Your having a bit of trouble because you're trying to solve an Inertia problem with non inertia measurements i.e. Front Weight  and Balance Weight.
    Why put a wheel on a balance scale to know how fast it will roll down a hill?
    With my software this problem is easily solved as it measures all the mass and all the leverage and gives a real Inertia number to work with.

    -chris



    ------------------------------
    Chernobieff Piano Restorations
    All the elements are known, and yet no combination there of creates life. Yet we are here.
    865-986-7720 (text only please)
    ------------------------------



  • 3.  RE: Baldwin SD Touchweight Quandry

    Posted 05-24-2023 11:20

    Check the position of the damper upstop rail.  When any given sharp is fully depressed, it should still be possible to slightly raise the damper more.

    I have on several occasions set the damper upstop rail by loosening it, lowering it, applying the damper pedal, then tightening it.  This has introduced problems for our piano users, because it did not end up providing adequate clearance.  A couple of instruments were particularly problematic.  Don't ask me how many hours I spent doing other things to try to correct the problem!  Heavy touch was the complaint.

    The February 2023 journal featured an article on the adjustment of the damper upstop rail that introduced to me the missing piece.  A slotted .020" punching is inserted between the pitman and the damper lift rail while the upstop rail is being adjusted, then removed.  On two of our pianos in particular, this has proved to be the magic bullet.



    ------------------------------
    Floyd Gadd RPT
    Regina SK
    (306) 502-9103
    ------------------------------



  • 4.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-24-2023 16:37

    Front Weight + Balance Weight is not an inertia measurement.  It is a useful and easily measured quantity that is associated with various combinations of Strike Weight and Ratio which are associated with inertial playing qualities.   



    ------------------------------
    David Stanwood RPT
    Stanwood Piano Innovations Inc.
    West Tisbury MA
    (508) 693-1583
    ------------------------------



  • 5.  RE: Baldwin SD Touchweight Quandry

    Posted 05-24-2023 18:13

    Estimating is not science, it's just good guessing. For example, picture two see saws side by side. One has two little kittens, the other two full grown elephants. We can easily estimate that the one with the kittens will be the faster see saw. But none of that tells us the actual calculated speeds of the see saws with either the kittens or the elephants. Inertia is mass times the radius squared and it is usually expressed in units of kg/m^2.or lb.ft^2. When you have an actual mathematical sum,  then all of the variable of masses and leverages in a piano action can be precisely expressed.

    -chris



    ------------------------------
    Chernobieff Piano Restorations
    All the elements are known, and yet no combination there of creates life. Yet we are here.
    865-986-7720 (text only please)
    ------------------------------



  • 6.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-24-2023 18:35

    Ah, very good grasshopper. Well, you are correct about the units of inertia, but levels of inertia can easily be inferred from static measurements.



    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 7.  RE: Baldwin SD Touchweight Quandry

    Posted 05-24-2023 18:55

    If that were true, then threads like this wouldn't exist.
    -chris



    ------------------------------
    Chernobieff Piano Restorations
    All the elements are known, and yet no combination there of creates life. Yet we are here.
    865-986-7720 (text only please)
    ------------------------------



  • 8.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-25-2023 16:03

    I believe the issue is primarily that some individuals are striving for relevance, although I personally am focused on following Nick Gravagne's Sage advice and reducing my neurotic tendencies. I suppose I'll have to be satisfied with that.

    The problem, Chris, is that no technicians use units of inertia, not even those capable of understanding it. Even individuals like the late Darrell Fandrich and certified engineer John Rhodes developed a concept unrelated to units of inertia, but rather something simpler using static measurements  

    David Stanwood's system, which many people utilize, also derives inertia from a series of static measurements. His objective is to achieve a specific inertia target by combining data such as front weight, strike weight, action leverage, and balance weight. These parameters, when met according to his system, result in a manageable level of inertia. It's worth noting that pianos inherently have higher inertia in the bass due to the decreasing mass of the hammers, but that's a separate issue. As a side note, for those interested in achieving a uniform level of inertia, it might be worth considering the addition of lead weights at opposite positions and equal values on the front and back of the keys to increase key inertia. However, currently we tend to use the minimum number of weights necessary to attain a specific balance weight. Consequently, the contribution of the key to the overall inertia is less significant compared to leverage and hammer mass.

    Therefore, we aim for specific strike weights with certain action ratios to achieve an acceptable level of inertia. If you're unfamiliar with the process, you can become a Stanwood licensed installer to learn and apply these techniques, which can be valuable credentials in the market. David Stanwood and others, including myself, have been generous in sharing this information and offering a practical approach without delving into relatively useless numerical calculations of inertia.

    While I appreciate your desire to demonstrate your engineering expertise, it holds little practical importance in what we actually do.



    ------------------------------
    David Love RPT
    www.davidlovepianos.com
    davidlovepianos@comcast.net
    415 407 8320
    ------------------------------



  • 9.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-25-2023 22:34

    https://www.youtube.com/watch?v=s7TPNK3SA7c&ab_channel=TouchWeightManagement




  • 10.  RE: Baldwin SD Touchweight Quandry

    Posted 05-26-2023 01:40

    Holy mischaracterization Batman!! And an out of the blue free insult too. Thank You David.

    I'm stating, the current systems (Stanwood, Gravagne, Fandrich) do not address inertia. The current methods use ( FW, BW, AR) which give false reads. Look at Popes first post. Both SW and BW failed. This happens because these measurements are indirect, and therefore confuse.
    BW= partial mass but no leverage info
    SW= partial mass but no leverage info
    AR= neither mass or leverage info
    FW= partial mass no leverage info.

    The Fandrich Rhodes method came the closest but has two flaws- the use of FW and only an inertia value for one note(the rest is assumed).

    I was intrigued by the inertia value, so i decided to make a system that incorporates inertia values for every note. So a year of R & D, then a year of writng a software program, a good month writing a manual. The charts I was getting from various actions is amazingly revealing. I sent the system out to several piano technicians to be vetted and to help make sure the instructions are clear.
    Now a couple techs that have ITW also have the other methods. And here is a neat discovery, it is reported that (on previously balanced actions)the gram difference of adjacent keys can be up to 30 grams and still be very hard for a pianist to distinguish. Especially in blind tests. This can be pulled off because of leverage. In fact, in one test, i used 200g right next to the balance to get 50g DW.  So the other systems can give a general idea of the level of inertia, but they cannot measure with precision from note to note. 

    So here's the neat part David. Since ITW uses a software program on a computer, it does ALL the math and calculations automatically. No Math skills required.

    As is so often the case, i was simply fortunate to gain from the previous experts who wrote articles on action balancing, inertia, and who created their own software. I was able to go farther forward by simplifying  the process (by eliminating many wasteful measurements) take more accurate measurements and created a new inertia value scoring system to accurately describe a piano touch level using 3 numbers(i.e. #1-78, #49- 75, #88- 68). The charts show the smoothness from note to note.
    Very Easy and Accurate!!

    -chris






    ------------------------------
    Chernobieff Piano Restorations
    All the elements are known, and yet no combination there of creates life. Yet we are here.
    865-986-7720 (text only please)
    ------------------------------



  • 11.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-24-2023 11:23

    John,
    I would check soundboard crown. The lack of crown can be a major factor contributing to lack of dynamic range. Also, check for down bearing.



    ------------------------------
    Roger Gable RPT
    Gable Piano
    Everett WA
    (425) 252-5000
    ------------------------------



  • 12.  RE: Baldwin SD Touchweight Quandry

    Posted 05-24-2023 12:41

    In my post above, I mentioned the damper lift rail, but I think I should have more correctly said the damper lift tray.

    Early damper timing can also contribute to a feeling of heaviness.

    If you've used the Stanwood measurements, you have already explored the question of friction.



    ------------------------------
    Floyd Gadd RPT
    Regina SK
    (306) 502-9103
    ------------------------------



  • 13.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-26-2023 11:16
    I haven't gotten through all the replies yet but am surprised that nobody has yet asked: 
    How many grams of friction? 

    (DW - UW) / 2 = Friction 

    If it's over 14g you likely have some repinning to do. Processing friction is preliminary to weigh off. If left undone it can give you skewed results.    
    6 swings coming to a pendulum stop (not a screeching halt) is what I shoot for. 

    Past that, if the hammers are too light (and it sounds like they might be) the piano will feel heavy but measure light, and the keys have few leads because otherwise the hammers won't return. 

    I seem to remember too that Baldwins in the SD6 SD10 family have a slotted whippen rail screw, making the convergence line adjustable? 

    All things to investigate. 
    I hope this helps and good luck! 






  • 14.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-26-2023 13:09

    Friction is low in this action. If I remember correctly C4 had 8g. Hammers we tested had 10 or more swings.

    As to that wippen rail, yes, we should check the spread. Does anyone have a number on how wide the spread should be on an SD1 or a method for deriving it?

    As to hammers being too light and feeling heavy, that's a new one to me. Would anyone care to elaborate?



    ------------------------------
    John Pope
    University of Kentucky School of Music
    Lexington, KY
    ------------------------------



  • 15.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-26-2023 13:29
    You said you had a balance weight of 38g. That's 14g friction, which is high. 

    Regarding light hammers, I would recommend my dear friend David Stanwood's method of adding a binder clip to the hammer shank, then using key leads and gram weights - like you would for new key set weigh off - to get the numbers you're looking for. (Which for me is 52g to 48g bass to treble). 

    If anyone wants to know more about the weigh off process, I'm happy to walk you through it.  







  • 16.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-26-2023 19:35

    John,

    What is the knuckle to center pin measurement? If it's less than 16mm you've got trouble.

    How does the jack line up under the knuckle at ideal rest position...is it a perfect 90° angle? This is the first place to look to determine if the spread is correct or not.

    What is the condition of whippen contact cushion? Indented, corroded, etc? If so, clean with starting fluid, brush with a wire brush, then apply a small amount of VS-PROFELT. Then bolster one with bushing cloth and see if there's any difference. 

    Peter Grey Piano Doctor 



    ------------------------------
    Peter Grey
    Stratham NH
    (603) 686-2395
    pianodoctor57@gmail.com
    ------------------------------



  • 17.  RE: Baldwin SD Touchweight Quandry

    Registered Piano Technician
    Posted 05-27-2023 07:02
    Peter,
    Thanks for that reminder about incorrect spread showing up as an unparallel jack to knuckle core relationship. They are parallel. Knuckle to pin distance is 17mm.

    As to wip cloth, these parts are not particularly worn but thanks for sharing your method. The starter fluid is a new one to me.